The shift device for the transmission of a motor vehicle is provided with a shift lever which is typically located in the center console. When there is no center console or the center console does not provide a space for installing the shift lever, the shift lever may also be provided adjacent to the steering column or on the instrument panel.
In a typical automatic transmission, the shift positions are arranged in the order of the P (parking) position, the R (reverse) position, the N (neutral) position and the D (drive position) in that other. Oftentimes, a special forward travel position is provided in addition to the D position, and is typically located next to the drive position on the other side of the N position. Such an additional forward travel position is called as the S (sport mode) position, the 2 (second) position and the L (low speed) position depending on the purpose thereof. In the case of an electric vehicle or a hybrid vehicle, the additional forward travel position may consist of the B (regenerative braking) position. As the special forward travel position is designed for a special purpose such as increasing the engine brake and improving the response of the vehicle, it is selected only under special circumstances. As the special forward travel position is located next to the D position, it is possible that the vehicle operator inadvertently selects the special forward travel position, and it may irritate the vehicle operator.
The conventional shift device for an automatic transmission is provided with an interlock that prevents an improper shifting to be made under certain conditions. For instance, the shift position cannot be moved from the P position unless the brake pedal is depressed. The shift position cannot be shifted from the N position unless a button fitted to the shift level is depressed.
The shift lever was traditionally connected to the automatic transmission via a mechanical link. In recent years, various proposals have been made to detect the displacement of the shift lever with an electric sensor, and transmit the detection signal of the electric sensor to the automatic transmission via a control unit. Such an arrangement is known as the shift by wire (SBW) system. In the shift device illustrated in FIGS. 9 and 10 of U.S. Pat. No. 7,971,498, a shift knob for rotational movement is surrounded by a C-shaped stopper member that restricts the rotation of the shift knob to a range defined by the gap in the stopper member. This range can be varied by turning the C-shaped stopper member around the shift knob.
JP 2010-090925A discloses a SBW shift device using a shift lever of a momentary switch type. According to this shift device, the shift lever is configured to return to the N position upon release of the shift lever. The desired shift change is effected by moving the shift lever away from the N position in the corresponding direction, and releasing the shift lever. In this shift device, to avoid the inadvertent shifting from the D position to the R position even though the vehicle operator intends to change the shift position to the N position, the time period required for recognizing the completion of the shift change is varied depending on the kind of the shift change.
In the invention disclosed in U.S. Pat. No. 7,971,498, the selected shift position can be determined independently from the angular position of the shift knob while the rotational range of the shift knob is variably restricted by the stopper member. According to this invention, even when the shift knob is placed at a position other than the P position when deactivating the vehicle, the P position may be automatically restored when restarting the engine. However, no arrangement is made for preventing an inadvertent selection of a shift position or a shift interlock under special conditions.
The invention disclosed in JP 2010-090925A is applicable only to a momentary switch type shift device, and not to a shift device using an endlessly rotatable shift knob.